The study will examine age-related changes in the relationship between social support and psychological distress following troublesome life changes in adulthood. Data will be drawn from a longitudinal study of a representative sample of 1100 Chicago-area adults aged 20 to 70, who were interviewed initially in 1972 and re-interviewed in 1976. The study's aim is to examine age-related changes in three areas: 1. the structure of social support systems--diversity, dependability, intimacy and frequency of contact with network members; 2. the function of support networks--types of assistance (advice, insight, emotional support, etc.) provided in response to environmental stressors; 3. the effectiveness of social support--the ability of support systems to reduce the distress of decrements in mental health following exposure to troublesome life events or persistent frustrations in major adult roles. The major hypothesis is that, structurally, the support network will become more constricted with age and, consequently, will be used less frequently, provide fewer resources, and therefore prove less effective in alleviating the stressful impact of major life changes. Multi-variate analysis techniques will help determine the extent to which the age differences observed are due to characteristics of support networks, types of environmental stressors encountered, or something intrinsic to aging itself.